In the manufacture of welded tubes, a bead is formed along the inside of the tube weld which must be removed. It is particularly desirable to achieve a removal that renders the bead indistinguishable from the inner diameter of the remainder of the tube. This is especially desirable where the tube will be reduced in diameter (and increased in length) for critical applications or a very smooth round surface is required with a minimum of machining (e.g., to be used for hydraulic cylinders).
It has been generally well known in these applications to use an inner diameter scarfing tool. These tools can take various forms, but the most useful are the mechanical and hydraulic scarfing tools which ride at the end of an impeder rod on rollers. The rollers are adjusted so that their contact with the inner walls of the tube provides alignment been the weld bead and the cutting tool mounted on the back end of the tool. Typically, the rollers have been preadjusted before scarfing to remove the optimum amount of bead.
In mechanical systems it is difficult to maintain the tolerances in the amount of removal because of cutting tool wear, variation of the strip thickness, and other out-of-adjustments that occur during the scarfing operation. More importantly, it is very difficult for mechanical tools to compensate for variations in the tube diameter or rough areas which the tool may encounter, e.g., butt welds, To overcome these difficulties, hydraulic tools were devised so that the application of pressure on one of the rollers would provided the compensation necessary to overcome the natural wear of the cutting tool, misadjustments or strip thickness.
While the hydraulic scarfing tools have provided a higher degree of precision to weld removal accuracy, they do not quickly adapt to abrupt changes in the inner diameter of the tube or provide the degree of accuracy needed for very severe tolerance specifications. Accordingly, it is an object of the present invention to provide an improved hydraulic scarfing tool which overcomes the limitations of the past tools and provides extremely fast response times and tight tolerances.